In a hybrid electric vehicle (HEV), either or both of an internal combustion engine and an electric traction motor are capable of supplying power to the wheels of the vehicle. One method of controlling the power supply to the wheels is to shut down or “pull-down” the engine during times that the engine is not needed to propel the vehicle in response to a power demand by a driver. When the driver power demand increases such that the electric motor cannot provide enough power to meet the demand, the engine may be activated or “pulled-up” to fulfill the power demand.
Unintentional pull-up/down of the engine may occur when the power demand is increased and then quickly decreased by the driver. This may occur in a situation, for example, in which the driver abruptly releases the accelerator pedal, and shortly thereafter abruptly depresses the pedal, or vice versa. In these situations, the engine may pull-up or pull-down unnecessarily. There is currently a need for a system that avoids unintentional pull-up and pull-down of the engine.